1 files changed, 44 insertions, 29 deletions

diff --git a/mm/memory.c b/mm/memory.c
index beabdefa6254..e046b7e4b530 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -776,8 +776,8 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
  * Do a quick page-table lookup for a single page.
  * mm->page_table_lock must be held.
  */
-static struct page *
-__follow_page(struct mm_struct *mm, unsigned long address, int read, int write)
+static struct page *__follow_page(struct mm_struct *mm, unsigned long address,
+                        int read, int write, int accessed)
 {
         pgd_t *pgd;
         pud_t *pud;
@@ -818,9 +818,11 @@ __follow_page(struct mm_struct *mm, unsigned long address, int read, int write)
                 pfn = pte_pfn(pte);
                 if (pfn_valid(pfn)) {
                         page = pfn_to_page(pfn);
-                        if (write && !pte_dirty(pte) && !PageDirty(page))
-                                set_page_dirty(page);
-                        mark_page_accessed(page);
+                        if (accessed) {
+                                if (write && !pte_dirty(pte) &&!PageDirty(page))
+                                        set_page_dirty(page);
+                                mark_page_accessed(page);
+                        }
                         return page;
                 }
         }
@@ -829,16 +831,19 @@ out:
         return NULL;
 }
 
-struct page *
+inline struct page *
 follow_page(struct mm_struct *mm, unsigned long address, int write)
 {
-        return __follow_page(mm, address, /*read*/0, write);
+        return __follow_page(mm, address, 0, write, 1);
 }
 
-int
-check_user_page_readable(struct mm_struct *mm, unsigned long address)
+/*
+ * check_user_page_readable() can be called frm niterrupt context by oprofile,
+ * so we need to avoid taking any non-irq-safe locks
+ */
+int check_user_page_readable(struct mm_struct *mm, unsigned long address)
 {
-        return __follow_page(mm, address, /*read*/1, /*write*/0) != NULL;
+        return __follow_page(mm, address, 1, 0, 0) != NULL;
 }
 EXPORT_SYMBOL(check_user_page_readable);
 
@@ -908,9 +913,13 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         pud = pud_offset(pgd, pg);
                         BUG_ON(pud_none(*pud));
                         pmd = pmd_offset(pud, pg);
-                        BUG_ON(pmd_none(*pmd));
+                        if (pmd_none(*pmd))
+                                return i ? : -EFAULT;
                         pte = pte_offset_map(pmd, pg);
-                        BUG_ON(pte_none(*pte));
+                        if (pte_none(*pte)) {
+                                pte_unmap(pte);
+                                return i ? : -EFAULT;
+                        }
                         if (pages) {
                                 pages[i] = pte_page(*pte);
                                 get_page(pages[i]);
@@ -935,11 +944,13 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 }
                 spin_lock(&mm->page_table_lock);
                 do {
+                        int write_access = write;
                         struct page *page;
-                        int lookup_write = write;
 
                         cond_resched_lock(&mm->page_table_lock);
-                        while (!(page = follow_page(mm, start, lookup_write))) {
+                        while (!(page = follow_page(mm, start, write_access))) {
+                                int ret;
+
                                 /*
                                  * Shortcut for anonymous pages. We don't want
                                  * to force the creation of pages tables for
@@ -947,13 +958,23 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                  * nobody touched so far. This is important
                                  * for doing a core dump for these mappings.
                                  */
-                                if (!lookup_write &&
-                                    untouched_anonymous_page(mm,vma,start)) {
+                                if (!write && untouched_anonymous_page(mm,vma,start)) {
                                         page = ZERO_PAGE(start);
                                         break;
                                 }
                                 spin_unlock(&mm->page_table_lock);
-                                switch (handle_mm_fault(mm,vma,start,write)) {
+                                ret = __handle_mm_fault(mm, vma, start, write_access);
+
+                                /*
+                                 * The VM_FAULT_WRITE bit tells us that do_wp_page has
+                                 * broken COW when necessary, even if maybe_mkwrite
+                                 * decided not to set pte_write. We can thus safely do
+                                 * subsequent page lookups as if they were reads.
+                                 */
+                                if (ret & VM_FAULT_WRITE)
+                                        write_access = 0;
+                                
+                                switch (ret & ~VM_FAULT_WRITE) {
                                 case VM_FAULT_MINOR:
                                         tsk->min_flt++;
                                         break;
@@ -967,14 +988,6 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 default:
                                         BUG();
                                 }
-                                /*
-                                 * Now that we have performed a write fault
-                                 * and surely no longer have a shared page we
-                                 * shouldn't write, we shouldn't ignore an
-                                 * unwritable page in the page table if
-                                 * we are forcing write access.
-                                 */
-                                lookup_write = write && !force;
                                 spin_lock(&mm->page_table_lock);
                         }
                         if (pages) {
@@ -1224,6 +1237,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         struct page *old_page, *new_page;
         unsigned long pfn = pte_pfn(pte);
         pte_t entry;
+        int ret;
 
         if (unlikely(!pfn_valid(pfn))) {
                 /*
@@ -1251,7 +1265,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
                         lazy_mmu_prot_update(entry);
                         pte_unmap(page_table);
                         spin_unlock(&mm->page_table_lock);
-                        return VM_FAULT_MINOR;
+                        return VM_FAULT_MINOR|VM_FAULT_WRITE;
                 }
         }
         pte_unmap(page_table);
@@ -1278,6 +1292,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         /*
          * Re-check the pte - we dropped the lock
          */
+        ret = VM_FAULT_MINOR;
         spin_lock(&mm->page_table_lock);
         page_table = pte_offset_map(pmd, address);
         if (likely(pte_same(*page_table, pte))) {
@@ -1294,12 +1309,13 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
 
                 /* Free the old page.. */
                 new_page = old_page;
+                ret |= VM_FAULT_WRITE;
         }
         pte_unmap(page_table);
         page_cache_release(new_page);
         page_cache_release(old_page);
         spin_unlock(&mm->page_table_lock);
-        return VM_FAULT_MINOR;
+        return ret;
 
 no_new_page:
         page_cache_release(old_page);
@@ -1991,7 +2007,6 @@ static inline int handle_pte_fault(struct mm_struct *mm,
         if (write_access) {
                 if (!pte_write(entry))
                         return do_wp_page(mm, vma, address, pte, pmd, entry);
-
                 entry = pte_mkdirty(entry);
         }
         entry = pte_mkyoung(entry);
@@ -2006,7 +2021,7 @@ static inline int handle_pte_fault(struct mm_struct *mm,
 /*
  * By the time we get here, we already hold the mm semaphore
  */
-int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
+int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
                 unsigned long address, int write_access)
 {
         pgd_t *pgd;